By 2010, the most recent year for which EIA has global data, U.S. emissions fell to 5.6 billion metric tons, while global emissions rose to 31.8 billion metric tons. Accordingly, the United States accounted for just 18 percent of global carbon dioxide emissions in 2010.

The first-quarter 2012 U.S. emissions numbers indicate the U.S. share will likely fall further to 15 percent of global emissions this year. ”